You will have to disconnect fuel lines and evap. hoses and drop the fuel tank. Be careful if it is full. You have to have the car up on jack stands with plenty of clearance. Be careful not to force it or you will break off the hose connections at the tank and then will have to buy the complete and very expensive assembly.
where is the fuel filter located on a 2003 Pontiac sunfire
It doesn't have one.
Under the car by the fuel tank
If the part number is the same and the configuration is the same then sure.
there isn't one
Inside the fuel tank. Must be dropped and removed from the top.
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The fuel filter on a 2002 Pontiac Sunfire is in the rear between the fuel tank and the rear axle. By the way its under the car and easy to change takes about 10 minutes.
In the fuel tank
I recommend changing it every 50,000 miles unless it is a permanent filter that requires no maintenance.